Display device

ABSTRACT

Disclosed is a display device including: a substrate; a first insulating film over the substrate, the first insulating film exposing a part of the substrate to provide an exposed surface to the substrate; a second insulating film in contact with the exposed surface and a first side surface of the first insulating film; and a first wiring over the second insulating film and in contact with the exposed surface, the first insulating film, and the second insulating film. The display device may further possess a third insulating film spaced from the second insulating film and in contact with the exposed surface. The first insulating film has a second side surface opposing the first side surface through the exposed surface. The third insulating film may be in contact with the second side surface, and the wiring may be located over and in contact with the third insulating film.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority from theprior Japanese Patent Application No. 2017-136016, filed on Jul. 12,2017, and the PCT Application No. PCT/JP2018/015426, filed on Apr. 12,2018, the entire contents of which are incorporated herein by reference.

FIELD

An embodiment of the present invention relates to a display device and amanufacturing method thereof. For example, an embodiment of the presentinvention relates to a display device having a light-emitting elementand a manufacturing method thereof.

BACKGROUND

A liquid crystal display device and an organic EL (Electroluminescence)display device are represented as an example of display devices. Thesedisplay devices possess a liquid crystal element or an organiclight-emitting element (hereinafter, referred to as a light-emittingelement) in each of a plurality of pixels formed over a substrate. Aliquid crystal element and a light-emitting element respectively have alayer including a compound exhibiting liquid crystallinity and a layer(hereinafter referred to as an electroluminescence layer or an EL layer)including an emissive organic compound between a pair of electrodes(cathode and anode) and are driven by applying a voltage or supplying acurrent between the electrodes.

Use of a substrate with flexibility as a substrate provides flexibilityto the whole of the display device, which enables production of adisplay device having a bent shape or a display device which can befreely deformed by a user. When a display device is bent, it is possibleto reduce an apparent area of a frame and supply a display device withexcellent designability by folding a substrate so that the portion(frame) which does not contribute to display overlaps with a displayregion (see Japanese Patent Application Publication No. 2012-128006).

SUMMARY

An embodiment of the present invention is a display device. The displaydevice includes: a substrate; a first insulating film over thesubstrate, the first insulating film exposing a part of the substrateproviding an exposed surface to the substrate; a second insulating filmin contact with the exposed surface and a first side surface of thefirst insulating film; and a first wiring over the second insulatingfilm and in contact with the exposed surface, the first insulating film,and the second insulating film.

An embodiment of the present invention is a display device. The displaydevice includes: a substrate having a first region, a second region, anda trench overlapping with a region between the first region and secondregion and having a first sidewall and a second sidewall facing eachother; a pair of first insulating films over the substrate and incontact with the substrate in the first region and the second region,respectively; a pair of second insulating films in the trench, the pairof second insulating films being spaced from each other and in contactwith the first sidewall and the second sidewall, respectively; and aplurality of wirings over and in contact with the pair of firstinsulating films and the pair of second insulating films, the pluralityof wirings being in contact with the substrate in the trench.

An embodiment of the present invention is a display device. The displaydevice includes: a substrate having a first region, a second region, anda third region sandwiched by the first region and the second region, apixel over the first region; a terminal over the second region; and anundercoat over the first region and the second region, the undercoatbeing arranged so that the substrate is exposed in the third region. Thesubstrate possesses a first step between the first region and the thirdregion, and a second step between the second region and the thirdregion. The display device further includes: a first filler in contactwith the first step; a second filler spaced from the first filler and incontact with the second step; and a plurality of wirings. The pluralityof wirings is located over the undercoat and is in contact with theundercoat in the first region and the second region and with the firstfiller, the second filler, and the substrate in the third region.

An embodiment of the present invention is a manufacturing method of adisplay device. The manufacturing method includes: forming an undercoatover a substrate having a first region, a second region, and a thirdregion between the first region and the second region; forming, in thefirst region, a transistor having a semiconductor film, a gateelectrode, and a gate insulating film between the semiconductor film andthe gate electrode; forming a first step between the first region andthe third region and a second step between the second region and thethird region by removing the undercoat in the second region to exposethe substrate; forming a first filler in contact with a first sidewallof the first step and a second filler spaced from the first filler andin contact with a second sidewall of the second step; forming a sourceelectrode and a drain electrode of the transistor in the first region;forming a terminal in the third region; and forming a plurality ofwirings in contact with the undercoat in the first region and the secondregion and in contact with the first filler, the second filler, and thesubstrate in the third region.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic top view of a display device according to anembodiment;

FIG. 2 is a schematic side view of a display device according to anembodiment;

FIG. 3 is an example of an equivalent circuit of a pixel of a displaydevice according to an embodiment;

FIG. 4 is a schematic cross-sectional view of a display device accordingto an embodiment;

FIG. 5 is a schematic cross-sectional view of a display device accordingto an embodiment;

FIG. 6 is a schematic cross-sectional view of a display device accordingto an embodiment;

FIG. 7A is a schematic top view of a display device according to anembodiment;

FIG. 7B is a schematic top view of a display device according to anembodiment;

FIG. 7C is a schematic top view of a display device according to anembodiment;

FIG. 8 is a schematic cross-sectional view of a display device accordingto an embodiment;

FIG. 9A is a schematic cross-sectional view of a display deviceaccording to an embodiment;

FIG. 9B is a schematic cross-sectional view of a display deviceaccording to an embodiment;

FIG. 10A is a schematic cross-sectional view of a display deviceaccording to an embodiment;

FIG. 10B is a schematic cross-sectional view of a display deviceaccording to an embodiment;

FIG. 11A is a schematic cross-sectional view of a display deviceaccording to an embodiment;

FIG. 11B is a schematic cross-sectional view of a display deviceaccording to an embodiment;

FIG. 12A is a schematic cross-sectional view of a display deviceaccording to an embodiment;

FIG. 12B is a schematic cross-sectional view of a display deviceaccording to an embodiment;

FIG. 13A is a schematic cross-sectional view of a display deviceaccording to an embodiment;

FIG. 13B is a schematic cross-sectional view of a display deviceaccording to an embodiment;

FIG. 14A is a schematic top view of a display device according to anembodiment;

FIG. 14B is a schematic top view of a display device according to anembodiment;

FIG. 15A is a schematic cross-sectional view for explaining amanufacturing method of a display device according to an embodiment;

FIG. 15B is a schematic cross-sectional view for explaining amanufacturing method of a display device according to an embodiment;

FIG. 16A is a schematic cross-sectional view for explaining amanufacturing method of a display device according to an embodiment;

FIG. 16B is a schematic cross-sectional view for explaining amanufacturing method of a display device according to an embodiment;

FIG. 17A is a schematic cross-sectional view for explaining amanufacturing method of a display device according to an embodiment;

FIG. 17B is a schematic cross-sectional view for explaining amanufacturing method of a display device according to an embodiment;

FIG. 18A is a schematic cross-sectional view for explaining amanufacturing method of a display device according to an embodiment;

FIG. 18B is a schematic cross-sectional view for explaining amanufacturing method of a display device according to an embodiment;

FIG. 19 is a schematic cross-sectional view for explaining amanufacturing method of a display device according to an embodiment;

FIG. 20 is a schematic cross-sectional view for explaining amanufacturing method of a display device according to an embodiment; and

FIG. 21 is a schematic cross-sectional view for explaining amanufacturing method of a display device according to an embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the embodiments of the present invention are explained withreference to the drawings. The invention can be implemented in a varietyof different modes within its concept and should not be interpreted onlywithin the disclosure of the embodiments exemplified below.

The drawings may be illustrated so that the width, thickness, shape, andthe like are illustrated more schematically compared with those of theactual modes in order to provide a clearer explanation. However, theyare only an example, and do not limit the interpretation of theinvention. In the specification and the drawings, the same referencenumber is provided to an element that is the same as that which appearsin preceding drawings, and a detailed explanation may be omitted asappropriate.

In the present specification and claims, when a plurality of films isformed by processing one film, the plurality of films may have functionsor rules different from each other. However, the plurality of filmsoriginates from a film formed as the same layer in the same process andhas the same layer structure and the same material.

Therefore, the plurality of films is defined as films existing in thesame layer.

In the specification and the claims, unless specifically stated, when astate is expressed where a structure is arranged “over” anotherstructure, such an expression includes both a case where the substrateis arranged immediately above the “other structure” so as to be incontact with the “other structure” and a case where the structure isarranged over the “other structure” with an additional structuretherebetween.

In the present specification, when a plurality of structural elementssimilar to one another is discriminately indicated, the structuralelements are expressed by using an underscore and a natural number aftera reference number. When all of the structural elements are indicated oran arbitrarily selected multiple thereof is expressed indiscriminately,only a reference number is used.

In the present specification and claims, an expression “a structuralbody is exposed from another structural body” means an aspect where aportion of the structural body is not covered by the other structuralbody and includes an aspect where the portion which is not covered bythe other structural body is covered by yet another structural body.

First Embodiment

A structure of a display device 100 according to an embodiment of thepresent invention is explained below.

1. Outline Structure

A schematic top view of the display device 100 is shown in FIG. 1. Thedisplay device 100 possesses a substrate 102 and a variety of patternedinsulating films, semiconductor films, and conductive films thereover. Aplurality of pixels 104 and driver circuits (gate-side driver circuits108 and source-side driver circuit 110) for driving the pixels 104 areformed by these insulating films, semiconductor films, and conductivefilms. The plurality of pixels 104 is periodically arranged and definesa display region 106. As described below, a display element is disposedin each pixel 104. Hereinafter, an example is explained in which alight-emitting element 130 is provided in the pixel 104 as a displayelement.

The gate-side driver circuits 108 and the source-side driver circuit 110are arranged outside the display region 106 (peripheral region). Avariety of wirings (not illustrated in FIG. 1) formed with patternedconductive films extends from the display region 106, the gate-sidedriver circuits 108, and the source-side driver circuit 110 to a side ofthe substrate 102 and is exposed at a vicinity of an edge portion of thesubstrate 102 to form terminals such as image-signal terminals 116 andpower-source terminals 118 and 120. These terminals are electricallyconnected to a flexible printed circuit substrate (FPC) 114. In theexample shown here, a driver IC 112 having an integrated circuit formedover a semiconductor substrate is mounted over the FPC 114. The functionof the source-side driver circuit 110 may be integrated with the driverIC 112, and the driver IC 112 may not be mounted over the FPC 114 butmay be mounted over the substrate 102. Image signals are supplied froman external circuit (not illustrated) through the driver IC 112 and FPC114 and transmitted to the gate-side driver circuits 108 and thesource-side driver circuit 110 through the image-signal terminals 116. Apower source supplied to the light-emitting elements 130 in the pixels104 is provided to the display device 100 through the FPC 114 and thepower-source terminals 118 and 120. A high potential (PVDD) is providedto the power-source terminals 120, while a potential (PVSS) lower thanthe PVDD is provided to the power-source terminals 118. Signals based onthese image signals and potentials are supplied to each pixel 104 withthe wirings 220 electrically connected to the terminals, by which thepixels 104 are controlled and operated.

Use of a substrate having flexibility as the substrate 102 provides thedisplay device 100 with flexibility. For example, folding the substrate102 between the terminals and the display region 106 so that the FPC 114and the terminals connected thereto overlap with the display region 106allows the formation of a three-dimensional structure as shown in a sideview of FIG. 2. At that time, a spacer 122 may be disposed to stabilizethe folded structure. At least a part of an outer circumference of thespacer 122 is covered by the substrate 102.

2. Structure of Pixel 2-1. Pixel Circuit

In each pixel 104, a pixel circuit including the light-emitting element130 is structured with a variety of patterned insulating films,semiconductor films, and conductive films. The structure of the pixelcircuit can be arbitrarily selected, and an example thereof isdemonstrated in FIG. 3 as an equivalent circuit.

The pixel circuit shown in FIG. 3 includes a driving transistor 140, afirst switching transistor 142, a second switching transistor 144, astorage capacitor 150, and a supplementary capacitor 152 in addition tothe light-emitting element 130. The light-emitting element 130, thedriving transistor 140, and the second switching transistor 144 areconnected in series between a high-potential power-source line 154 and alow-potential power-source line 156. The PVDD and PVSS are respectivelysupplied to the high-potential power-source line 154 and thelow-potential power-source line 156.

In the present embodiment, the driving transistor 140 is assumed to bean n-channel type, and input-output terminals on a side of thehigh-potential power-source line 154 and a side of the light-emittingelement 130 are defined as a drain and a source, respectively. The drainof the driving transistor 140 is electrically connected to thehigh-potential power-source line 154 through the second switchingtransistor 144, and the source thereof is electrically connected to apixel electrode 184 of the light-emitting element 130.

A gate of the driving transistor 140 is electrically connected to afirst signal line VSL through the first switching transistor 142.Operation (on/off) of the first switching transistor 142 is controlledwith a scanning signal SG supplied to a first scanning signal line SLAconnected to a gate thereof. When the first switching transistor 142 ison, a potential of the first signal line VSL is provided to the gate ofthe driving transistor 140. An initialization signal Vini and an imagesignal Vsig are provided to the first signal line VSL at a predeterminedtiming. The initialization signal Vini is a signal providing aninitialization potential with a constant level. The on/off of the firstswitching transistor 142 is controlled at a predetermined timing whilesynchronizing with the first signal line VSL, and a potential based onthe initialization signal Vini or the image signal Vsig is provided tothe gate of the driving transistor 140.

A second signal line VRS is electrically connected to the drain of thedriving transistor 140. A reset potential Vrst is supplied to the secondsignal line VRS through a third switching transistor 146. A timing atwhich the reset signal Vrst is applied through the third switchingtransistor 146 is controlled by a reset signal RG provided to a thirdsignal line SLC.

The storage capacitor 150 is disposed between the source and drain ofthe driving transistor 140. One terminal of the supplementarycapacitor152 is connected to the source of the driving transistor 140,and the other terminal is connected to the high-potential power-sourceline 154. The supplementary capacitor 152 may be formed so that theother terminal is connected to the low-potential power-source line 156.The storage capacitor 150 and the supplementary capacitor 152 areprovided to maintain a source-drain voltage Vgs corresponding to theimage signal Vsig when the image signal Vsig is provided to the gate ofthe driving transistor 140.

The source-side driver circuit 110 outputs the initialization signalVini or the image signal Vsig to the first signal line VSL. Thegate-side driver circuits 108 output the scanning signal SG, a scanningsignal BG, and the reset signal RG to the first scanning line SLA, asecond scanning line SLB, and the third signal line SLC.

Although it is necessary to dispose the driving transistor 140 and thefirst switching transistor 142 in each pixel 104 shown in FIG. 1, thesecond switching transistor 144 may be shared by the plurality of pixels104 close to one another. Specifically, the second switching transistor144 may be shared by the plurality of pixels 104 which belong to thesame scanning line and which are close to one another. Additionally,although the third switching transistor 146 is arranged in the gate-sidedriver circuits 108 in the example shown in FIG. 3, the third switchingtransistor 146 may be formed in each pixel circuit or may be shared bythe plurality of pixels 104 close to one another similar to the secondswitching transistor 144.

2-2. Cross-Sectional Structure

A cross-sectional structure of the pixel 104 is explained using thedrawings. Cross-sectional structures of the driving transistor 140, thestorage capacitor 150, the supplementary capacitor 152, and thelight-emitting element 130 of the pixel circuits of the adjacent twopixels 104 formed over the substrate 102 are illustrated in FIG. 4.[0029]

Each element included in the pixel circuit is disposed over thesubstrate 102 through an undercoat 160. The driving transistor 140includes a semiconductor film 162, a gate insulating film 164, a gateelectrode 166, a drain electrode 172, and a source electrode 174. Thegate electrode 166 is arranged to intersect at least a part of thesemiconductor film 162 via the gate insulating film 164, and a channelis formed in a region where the gate electrode 166 overlaps with thesemiconductor film 162. The semiconductor film 162 further possesses adrain region 162 a and a source region 162 b sandwiching the channel.

A capacitor electrode 168 existing in the same layer as the gateelectrode 166 is formed to overlap with the source region 162 b throughthe gate insulating film 164. An interlayer insulating film 170 isdisposed over the gate electrode 166 and the capacitor electrode 168.Openings reaching the drain region 162 a and the source region 162 b areformed in the interlayer insulating film 170 and the gate insulatingfilm 164, and the drain electrode 172 and the source electrode 174 arearranged so as to cover the openings. A part of the source electrode 174overlaps with a part of the source region 162 b and the capacitorelectrode 168 through the interlayer insulating film 170, and thestorage capacitor 150 is structured by the part of the source region 162b, the gate insulating film 164, the capacitor electrode 168, theinterlayer insulating film 170, and the part of the source electrode174.

A planarization film 176 is further provided over the driving transistor140 and the storage capacitor 150. The planarization film 176 has anopening reaching the source electrode 174, and a connection electrode178 covering this opening and a part of a top surface of theplanarization film 176 is formed to be in contact with the sourceelectrode 174. The supplementary capacitor electrode 180 is furtherdisposed over the planarization film 176. The connection electrode 178and the supplementary capacitor electrode 180 may be simultaneouslyformed and can exist in the same layer. A capacitor insulating film 182is formed to cover the connection electrode 178 and the supplementarycapacitor electrode 180. The capacitor insulating film 182 does notcover a part of the connection electrode 178 in the opening of theplanarization film 176 to expose a top surface of the connectionelectrode 178. This structure enables electrical connection between thepixel electrode 184 formed over the connection electrode 178 and thesource electrode 174 via the connection electrode 178. An opening 188may be formed in the capacitor insulating film 182 to allow contact of apartition wall 186 formed thereover with the planarization film 176.Impurities in the planarization film 176 can be removed through theopening 188, thereby improving reliability of the light-emitting element130. Note that the formation of the connection electrode 178 and theopening 188 is optional.

The pixel electrode 184 is disposed over the capacitor insulating film182 to cover the connection electrode 178 and the supplementarycapacitor electrode 180. The capacitor insulating film 182 is sandwichedby the supplementary capacitor electrode 180 and the pixel electrode184, and the supplementary capacitor 152 is configured by thisstructure. The pixel electrode 184 is shared by the supplementarycapacitor 152 and the light-emitting element 130.

The partition wall 186 is provided over the pixel electrode 184 to coveran edge portion of the pixel electrode 184. An EL layer 190 and anopposing electrode 198 thereover are arranged so as to cover the pixelelectrode 184 and the partition wall 186.

The EL layer 190 may be composed of a plurality of layers and is formedby combining a variety of functional layers such as a carrier-injectionlayer, a carrier-transporting layer, an emission layer, acarrier-blocking layer, and an exciton-blocking layer. The structure ofthe EL layer 190 may be the same in all of the pixels 104, or the ELlayer 190 may be formed so that a part of the structure is differentbetween the adjacent pixels 104. In FIG. 4, a hole-transporting layer192, an emission layer 194, and an electron-transporting layer 196 areillustrated as the typical functional layers.

A protection film (hereinafter, referred to as a passivation film) 200is arranged over the light-emitting elements 130 to protect thelight-emitting elements 130. The structure of the passivation film 200can be arbitrarily selected, and a stacked structure including a firstlayer 202 containing an inorganic compound, a second layer 204containing an organic compound, and a third layer 206 containing aninorganic compound may be applied as shown in FIG. 4.

A film 210 (hereinafter, referred to as a resin film) including a resinis disposed over the passivation film 200. The display device 100further possesses supporting films 126 and 128 sandwiching the structurefrom the substrate 102 to the resin film 210, and appropriate physicalstrength is provided by the supporting films 126 and 128.

The supporting films 126 and 128 are respectively fixed to the substrate102 and the resin film 210 with an adhesive layer which is notillustrated.

As described below in detail, the undercoat 160, the gate insulatingfilm 164, the interlayer insulating film 170, the capacitor insulatingfilm 182, the first layer 202, and the third layer 206 are each aninsulating film and include a film including a silicon-containinginorganic compound such as silicon nitride, silicon oxide, siliconnitride oxide, and silicon oxynitride. The films including asilicon-containing inorganic compound may be stacked in each insulatingfilm. Therefore, these insulating films each include an inorganiccompound containing silicon as a main structural element.

3. Terminals and Wirings

FIG. 5 schematically shows an example of a cross-sectional structure inwhich the region from an edge portion of the display region 106 (lowerportion of the display region 106 in FIG. 1) to the power-sourceterminals 118 and 120 and the image-signal terminals 116 is at thecenter. Here, the cross-sections of a part of the display region 106,the source-side driver circuit 110, the power-source terminal 118, andthe wiring 220 electrically connecting the display region 106 to thepower-source terminal 118 are illustrated.

As shown in FIG. 5, the supporting film 126 is divided into two portionsby removing a part thereof, and a lower surface of the substrate 102 isexposed between the divided portions. The part where the supporting film126 is removed has high flexibility, and the display device 100 can befolded by utilizing this part as shown in FIG. 2.

Semiconductor elements such as a transistor are provided in thesource-side driver circuit 110, and a variety of circuits such as ananalogue circuit are structured by the semiconductor elements. Theopposing electrode 198 extends from the display region 106 to the edgeportion of the substrate 102 and is electrically connected to the wiring220 in an opening formed in the planarization film 176. Morespecifically, the wiring 220 is formed so as to be located between theinterlayer insulating film 170 and the planarization film 176, that is,to exist in the same layer as the source electrode 174 and the drainelectrode 172 in the pixel 104. The planarization film 176 has theopening reaching the wiring 220 between the source-side driver circuit110 and the power-source terminal 118, and a contact electrode 222including a first contact electrode 222 a and a second contact electrode222 b over the first contact electrode 222 a are disposed so as to coverthis opening. The opposing electrode 198 is electrically connected tothe wiring 220 through the second contact electrode 222 b and the firstcontact electrode 222 a. The wiring 220 forms the power-source terminal118 at the vicinity of the edge portion of the substrate 102. A surfaceof the power-source terminal 118 is covered with a protection electrode222 c existing in the same layer as the first contact electrode 222 a.

4. Filler

An enlarged view of FIG. 5 in which the wiring 220 is at the center isshown in FIG. 6. As shown in FIG. 6, the undercoat 160 is partly removedto be divided into two portions, providing the substrate 102 with anexposed surface exposed from the undercoat. Here, the region in whichthe substrate 102 is exposed from the undercoat 160 is referred to as athird region 218, and the regions in which the undercoat 160 exist arereferred to as a first region 214 and a second region 216. The displayregion 106, the source-side driver circuit 110, and the contactelectrode 222 are located in the first region 214, while the variety ofterminals including the power-source terminal 118 is located in thesecond region 216.

A thickness of the substrate 102 in the third region 218 is smaller thanthat in other regions. That is, a trench 132 overlapping with a regionbetween the first region 214 and the second region 214, i.e., the thirdregion 218, is formed in the substrate 102. Although the undercoat 160,the gate insulating film 164, the interlayer insulating film 170, andthe planarization film 176 are arranged over the substrate 102, theseinsulating films are removed in the trench 132. Namely, these insulatingfilms are not disposed in the third region 218. Side surfaces of thegate insulating film 164 and the interlayer insulating film 170 mayoverlap with a top surface of the undercoat 160 as shown in FIG. 6 orexist in the same plane as the side surfaces of the undercoat 160.

The trench 132 is structured by the sidewalls (first sidewall 134 andsecond sidewall 136) opposing each other and the top surface of thesubstrate 102 between the first sidewall 134 and the second sidewall136. A step (first step) is formed by the first sidewall 134 between thefirst region 214 and the third region 218, and a step (second step) isformed by the second sidewall 136 between the second region 216 and thethird region 218. These sidewalls may be located in the same plane asthe side surfaces of the undercoat 160 or do not have to be in alignmentwith the side surfaces of the undercoat 160.

The display device 100 further possesses a pair of fillers (first filler230 and second filler 232) in the trench 132. The fillers are insulatingfilms including a polymer such as an epoxy resin and an acrylic resin.Therefore, the fillers are organic compounds and contain carbon, oxygen,and hydrogen as main structural elements. The first filler 230 is incontact with the first step. That is, the first filler 230 is in contactwith the substrate 102 and the first sidewall 134 in the trench 132. Thesecond filler 232 is in contact with the second step. That is, thesecond filler 232 is spaced from the first filler 230 and in contactwith the substrate 102 and the second sidewall 136 in the trench 132.The first filler 230 and the second filler 232 may be in contact with orspaced from the side surfaces of the undercoat 160. It is preferred toform the first filler 230 and the second filler 232 so as not to be incontact with the top surface of the undercoat 160.

The wiring 220 is formed over the first filler 230 and the second filler232 in the trench 132 and in contact with the first filler 230, thesecond filler 232, and the substrate 102. The wiring 220 is not incontact with the first sidewall 134 and the second sidewall 136 due tothe first filler 230 and the second filler 232. The wiring 220 isfurther in contact with the side surface of the undercoat 160. When theside surfaces of the gate insulating film 164 and the interlayerinsulating film 170 overlap with the top surface of the undercoat 160,the wiring 220 is in contact with the top surface of the undercoat 160,the side surface of the gate insulating film 164, and the side surfaceof the interlayer insulating film 170 between the first sidewall 134 andthe display region 106 and between the second sidewall 136 and thepower-source terminal 118.

A schematic top view of a boundary between the first region 214 and thethird region 218 and the vicinity thereof is shown in FIG. 7A to FIG.7C. Here, a layout of the undercoat 160, the first filler 230, theinterlayer insulating film 170, and the wirings 220 is illustrated. Asdemonstrated in FIG. 7A, the first filler 230 may be arranged in astripe form along the first sidewall 134 (that is, along the sidesurface of the undercoat 160). In this case, the first filler 230 may becontinuous between the long sides of the substrate 102 opposing eachother or may be partly divided. Alternatively, as shown in FIG. 7B, thefirst filler 230 may be formed in an island form so as to be distributedalong the first sidewall 134. In this case, it is preferred that atleast the first filler 230 located under the wiring 220 be continuousacross the entire width of the wiring 220. Although not illustrated, thesame is applied to the second filler 232.

In the examples shown in FIG. 7A and FIG. 7B, the first sidewall 134,the side surface of the undercoat 160, and the side surface of theinterlayer insulating film 170 are formed to be parallel to the shortside of the substrate 102. However, these sidewall and side surfaces mayhave a curve in a plane parallel to the top surface of the substrate102. That is, these sidewall and side surfaces may have a curved shapein a plane view. For example, as shown in FIG. 7C, the first sidewall134, the side surface of the undercoat 160, and the side surface of theinterlayer insulating film 170 each may have a curved shape betweenadjacent wirings 220 and provide a straight line in a region overlappingwith the wiring 220 in the plane parallel to the top surface of thesubstrate 102. In this case, the first filler 230 and the second filler232 also have a curved shape in the plane parallel to the top surface ofthe substrate 102. The formation of such shapes enables reduction of aprobability of a short circuit between the wirings 220 even though anetching residue of the wirings 220 is attached to the first sidewall134, the side surface of the undercoat 160, or the side surface of theinterlayer insulating film 170 because the distances between theadjacent wirings 220 along the first sidewall 134, the side surface ofthe undercoat 160, and the side surface of the interlayer insulatingfilm 170 are increased.

The surfaces on which the first filler 230 and the second filler 232 arein contact with the wiring 220 are inclined from the first sidewall 134,the second sidewall 136, or the top surface of the substrate 102 asshown in FIG. 6. These surfaces may be a plane surface or a curvedsurface as shown in FIG. 8. Furthermore, as shown in FIG. 9A and FIG.9B, the first sidewall 134 and the second sidewall 136 may enter underthe undercoat 160. That is, a structure (overhang structure) in whichthe side surface of the undercoat 160 overlaps with the trench 132 maybe formed by side-etching the substrate 102. In this case, the firstfiller 230 and the second filler 232 are formed so as to fill a gapbetween the top surface of the substrate 102 and the undercoat 160 andto partly overlap with the undercoat 160. The first sidewall 134 and thesecond sidewall 136 may have a curved shape in a cross-sectionperpendicular to the top surface of the substrate 102.

As described above, the third region 218 in which the undercoat 160, thegate insulating film 164, and the interlayer insulating film 170 areremoved is provided between the display region 106 and the terminals(power-source terminals 118 and 120 and the image-signal terminals 116)of the display device 100. In addition, the trench 132 overlapping withthe third region 218 is formed in the substrate 102. Therefore, thethird region 218 is more flexible than other regions, and the displaydevice 100 can be readily folded in this region.

However, in the case where these insulating films are removed and thetrench 132 is formed, the wirings 220 are readily disconnected due totheir steps because relatively large steps are generated from thedisplay region 106 to the terminals. Particularly, when the displaydevice 100 is folded by utilizing the third region 218, disconnection ofthe wirings 220 is promoted because a large stress is applied to thewirings 220 at the vicinity of these steps. For example, a large stressis applied to the wirings 220 over the first sidewall 134 and the secondsidewall 136, and therefore, the disconnection readily occurs. Suchdisconnection frequently occurs particularly at the portion where theundercoat 160 has the aforementioned overhang structure at the terminalportion of the trench 132.

In contrast, the display device 100 described in the present embodimentpossesses the fillers in contact with the first sidewall 134, the secondsidewall 136, and the substrate 102 in the trench 132. The fillers arecapable of particularly reducing the steps caused by the first sidewall134 and the second sidewall 136 and decreasing the variation in across-sectional shape which occurs from the undercoat 160 to the trench132. Hence, the stress applied to the wirings 220 when folding thedisplay device 100 is decreased, and the disconnection can besuppressed.

Moreover, in the case where the display device 100 has the overhangstructure, an etching residue tends to be left in the gap between thetop surface of the substrate 102 and the undercoat 160 when the wirings220 are formed with etching, which may cause a short circuit between thewirings. However, the gap is filled with the filler, which prevents theshort circuit between the wirings. Therefore, implementation of thepresent embodiment provides high reliability to the display device 100.

Second Embodiment

In the First Embodiment, an explanation is made for the display device100 in which the steps generated by the sidewalls (first sidewall 134and the second sidewall 136) of the trench 132 formed in the substrate102 and the side surface of the undercoat 160 are decreased by thefillers (the first filler 230 and the second filler 232). The ability ofthe fillers to decrease the steps is also effective to decrease thesteps formed between a variety of insulating films or the steps formedin the insulating films. In the present embodiment, a modified exampleis described in which the fillers are disposed to decrease the stepsbetween the insulating films formed over the substrate 102.

For example, the display device 100 may possess a third filler 234 and afourth filler 236 in addition to or instead of the first filler 230 andthe second filler 232 as shown in FIG. 10A and an enlarged view (FIG.10B) of the region surrounded by the dotted circle. More specifically,the third filler 234 is in contact with the top surface of the undercoat160, the side surfaces of the gate insulating film 164 and theinterlayer insulating film 170, and the wiring 220 in the first region214. In a similar way, the fourth filler 236 is in contact with the topsurface of the undercoat 160, the side surfaces of the gate insulatingfilm 164 and the interlayer insulating film 170, and the wiring 220 inthe second region 216. In this case, the top surface of the undercoat160 may be partly exposed from the third filler 234 and the fourthfiller 236, or the whole of the top surface of the undercoat 160 may becovered by the third filler 234 and the fourth filler 236.

Alternatively, the undercoat 160 may have a first layer 160 a, a secondlayer 160 b, and a third layer 160 c, and a side surface of the thirdlayer 160 c may overlap with the second layer 160 b and the first layer160 a in the first region 214 and the second region 216 as shown in FIG.11A and an enlarged view (FIG. 11B) of the region surrounded by thedotted circle. As shown in FIG. 11B, the side surface of the third layer160 c may be coplanar with the side surfaces of the gate insulating film164 and the interlayer insulating film 170, or the side surfaces of thegate insulating film 164 and the interlayer insulating film 170 mayoverlap with a top surface of the third layer 160 c. Such a structuretends to be readily formed when the second layer 160 b and the thirdlayer 160 c include materials with a different etching rate. The thirdfiller 234 is in contact with a top surface of the second layer 160 band the side surface of the third layer 160 c in the first region 214and in contact with the wiring 220. In a similar way, the fourth filler236 is in contact with the top surface of the second layer 160 b and theside surface of the third layer 160 c in the second region 216 and incontact with the wiring 220.

Alternatively, in a case where the stack of the insulating film 170 andthe gate insulating film 164 forms a step, the third filler 234 and thefourth filler 236 may be provided so as to be in contact with a part ofthese insulating films as shown in FIG. 12A and an enlarged view (FIG.12B) of the region surrounded by the dotted circle. For example, in acase where the interlayer insulating film 170 is a stacked film of afirst layer 170 a and a second layer 170 b and a sidewall of the firstlayer 170 a overlaps with a top surface of the gate insulating film 164,the third filler 234 and the fourth filler 236 may be formed so as to bein contact with the first layer 170 a. Specifically, the third filler234 is in contact with the top surface of the gate insulating film 164,the side surface of the first layer 170 a, and the wiring 220 in thefirst region 214. In a similar way, the fourth filler 236 is in contactwith the top surface of the gate insulating film 164, the side surfaceof the first layer 170 a, and the wiring 220 in the second region 216.The gate insulating film 164 may be exposed from the first layer 170 a,or the whole of the top surface which is not in contact with the firstlayer 170 a may be covered by the third filler 234 and the fourth filler236.

Note that, the trench 132 may not be formed in the substrate 102. Forexample, the top surface of the substrate 102 in the third region 218may be coplanar with that in the first region 214 and the second region216 as shown in FIG. 13A and an enlarged view (FIG. 13B) of a part ofFIG. 13A. Namely, the thickness of the substrate 102 may be the same inthe first region 214, the second region 216, and the third region 218.

Similar to the first filler 230 and the second filler 232, the thirdfiller 234 and the fourth filler 236 are arranged parallel to the shortside of the substrate 102 so as to extend along the interlayerinsulating film 170 (or the gate insulating film 164) as shown in FIG.14A. Although not illustrated, the third filler 234 and the fourthfiller 236 may be arranged in an island form. Alternatively, the thirdfiller 234 and the fourth filler 236 may be formed to have a curve inthe plane parallel to the top surface of the substrate 102 as shown inFIG. 14B. In the example demonstrated in FIG. 14B, the first sidewall134, the side surface of the undercoat 160, and the side surface of theinterlayer insulating film 170 have a curved shape between the adjacentwirings 220 in the plane parallel to the top surface of the substrate102 and possess a straight shape in a region overlapping with the wiring220. The first filler 230 and the third filler 234 also possess a curvedshape in the plane parallel to the top surface of the substrate 102 soas to extend along the first wall 134, the side surface of the undercoat160, and the side surface of the interlayer insulating film 170.

An explanation of other structures will be omitted because they are thesame as or similar to those of the First Embodiment.

Similar to the First Embodiment, implementation of the presentembodiment allows the steps to be decreased even though the steps aregenerated between the insulating films provided over the substrate 102due to the difference in etching rate therebetween. As a result, it ispossible to prevent disconnection of the wirings formed over theinsulating films even if the display device 100 is deformed.Additionally, in a case where the overhang structure is formed betweenthe insulating films, the step therebetween can be filled with thefiller. Hence, a display device with high reliability can be produced.

Third Embodiment

In the present embodiment, a manufacturing method of the display device100 is described. Here, a manufacturing method of the display device 100having the structure shown in FIG. 9A is explained as an example byusing FIG. 15A to FIG. 21. Each of FIG. 15A to FIG. 20B contains twodrawings, and those on the left side are schematic cross-sectional viewsof the pixel 104, while those on the right side are schematiccross-sectional views in which the second region 216 is centered. Anexplanation of the contents which overlap with those in the First andSecond Embodiments may be omitted.

As shown in FIG. 15A, the substrate 102 is first formed over asupporting substrate 103. The supporting substrate 103 supports avariety of insulating films, conductive films, and semiconductor filmsincluded in the display device 100 during the manufacturing process ofthe display device 100 and may contain glass or quartz. The substrate102 is a flexible substrate and contains a polymer such as a polyimide,a polyamide, and a polycarbonate. The substrate 102 is formed over thesupporting substrate 103 with a wet-type film-formation method such asan ink-jet method, a spin-coating method, and a printing method or alamination method. When flexibility is not provided to the displaydevice 100, the substrate 103 may be used instead of the substrate 102.

Next, the undercoat 160 is formed over the substrate 102 so as to have asingle-layer structure or a stacked-layer structure. The undercoat 160is provided over the whole of the surface of the substrate 102. Here,stacked layers of the first layer 160 a to the third layer 160 c aredemonstrated as the undercoat 160, and a silicon-oxide film, asilicon-nitride film, and a silicon-oxide film may be respectively usedfor the first layer 160 a to the third layer 160 c, for example. In thiscase, the first layer 160 a is formed to improve adhesion to thesubstrate 102, the second layer 160 b is provided as a blocking filmagainst impurities such as water, and the third layer 160 c is providesas a blocking film to prevent diffusion of hydrogen atoms included inthe second layer 160 b. Although not illustrated, a light-shielding filmmay be formed in a region over which the transistors are to be formedbefore forming the undercoat 160. Here, a silicon-oxide film is a filmcontaining silicon and oxygen as main components, while asilicon-nitride film is a film containing silicon and nitrogen as maincomponents.

Next, the transistors and the like in the pixel circuit are fabricatedover the undercoat 160 (FIG. 15B). Here, although the formation of then-channel type driving transistor 140 having polysilicon in thesemiconductor film 162 as a transistor and the storage capacitor 150 isdescribed as an example, a p-channel type transistor may besimultaneously formed. The semiconductor film 162, the gate insulatingfilm 164, the gate electrode 166, and the capacitor electrode 168 aresequentially formed over the undercoat 160. The semiconductor film 162has a structure in which not only a channel region 162 c overlappingwith the gate electrode 166, the drain region 162 a, and the sourceregion 162 b but also low-concentration impurity regions 162d arearranged between the channel region 162 c and the drain region 162 a andbetween the channel region 162 c and the source region 162 b. The gateinsulating film 164 includes a silicon-containing inorganic compound,and a silicon-oxide film or the like is employed. The gate electrode 166and the capacitor electrode 168 are prepared by using a wiring (firstwiring) including a metal selected from a variety of metals or an alloythereof, and the first wiring possesses a stacked structure ofmolybdenum and tungsten, for example. The capacitor electrode 168 existsin the same layer as the gate electrode 166 and is used to fabricate thestorage capacitor 150 as well as the gate insulating film 164 and thesource region 162 b.

The interlayer insulating film 170 is formed over the gate electrode 166and the capacitor electrode 168 (FIG. 15B). The interlayer insulatingfilm 170 is also prepared across the first region 214, the third region218, and the second region 216. Although the interlayer insulating film170 having a single-layer structure is illustrated in FIG. 15B, theinterlayer insulating film 170 may be formed by stacking asilicon-nitride film and a silicon-oxide film.

After that, patterning is performed to partly remove the interlayerinsulating film 170 and the gate insulating film 164, thereby exposingthe undercoat 160 in the third region 218 (FIG. 16A). At that time, theopenings for exposing the drain region 162 a and the source region 162 bare simultaneously formed.

Next, a region where the trench 132 is not formed is covered with aresist mask which is not illustrated, and the exposed undercoat 160 isremoved with etching. At that time, it is preferred to performover-etching to ensure removal of the undercoat 106 with etching in thethird region 218. With this process, a part of the substrate 102 isremoved, resulting in the trench 132 in the third region 218. Etchingconditions may be appropriately selected. For example, conditionsproviding the overhang structure shown in FIG. 16B may be selected, orconditions allowing the undercoat 160 to be removed but inhibiting theformation of the trench 132 may be selected. Selection of the latterconditions provides the structure shown in FIG. 13A and FIG. 13B.Alternatively, the trench 132 may not be formed in the step of removingthe undercoat 160 with etching but may be formed by removing a part ofthe substrate 102 in the step of removing the resist mask by sequentialashing.

Although not illustrated, the removal of the undercoat 160 and theformation of the trench 132 may be carried out simultaneously with theformation of the openings for exposing the drain region 162 a and thesource region 162 b.

Next, the first filler 230 and the second filler 232 are formed.Specifically, oligomers providing an acrylic resin or an epoxy resin isgasified under a reduced pressure or atomized, and the substrate 102 isexposed to the vapor of the oligomers (resin evaporation). At that time,the substrate 102 may be sprayed with the vapor of the oligomers usingnitrogen or argon as a carrier gas. Due to the capillary phenomenon, theoligomers attached to the substrate 102 is preferentially disposed onthe first sidewall 134 and the second sidewall 136, and the gap betweenthe substrate 102 and the undercoat 160 formed at the vicinity of thefirst sidewall 134 and the second sidewall 136 are preferentiallycharged with the oligomers attached to the substrate 102. Therefore, theoligomers can be locally and selectively formed on the first sidewall134, the second sidewall 136, and in the gap formed at the vicinitythereof without using a mask by controlling the evaporation conditions(pressure and time of evaporation, heating temperature of the oligomers,and the like). After that, the oligomers are cured by a heatingtreatment or light irradiation to form the first filler 230 and thesecond filler 232, by which the overhang structure is covered by thefirst filler 230 and the second filler 232 (FIG. 17A). Note that, ifnecessary, the resin evaporation may be carried out while shielding theportion where the oligomers are not to be applied by using a shadowmask. Additionally, when the oligomers are attached to an unnecessaryportion, the unnecessary oligomers and the resin derived from theoligomers may be removed with an ashing treatment in the presence of agas including oxygen.

If the oligomers are applied in the openings formed over the drainregion 162 a and the source region 162 b during the resin evaporationand the electrical connection with the drain electrode 172 and thesource electrode 174 formed in the openings cannot be achieved, thefirst filler 230 and the second filler 232 may be formed using a shadowmask or may be formed after covering the openings with a resist mask.

Next, a conductive layer is formed using a second wiring and then etchedto prepare the drain electrode 172, the source electrode 174, and thewiring 220 (FIG. 17B). The second wiring may be also formed as a stackof a plurality of metal layers, and a three-layer stacked structure oftitanium/aluminum/titanium may be employed. With this process, thewiring 220 comes into contact with the substrate 102, the first filler230, and the second filler 232 in the trench 132. At the same time, apart of the source electrode 174 is arranged to overlap with thecapacitor electrode 168, by which the storage capacitor 150 is formedwith the source region 162 b, the gate insulating film 164, thecapacitor electrode 168, the interlayer insulating film 170, and a partof the source electrode 174. The wiring 220 extends to the second region216 and forms the power-source terminal 118 for connecting the FPC 114.

After that, the planarization film 176 is prepared so as to cover thedriving transistor 140, the storage capacitor 150, and the wiring 220(FIG. 17B). An organic material such as a photosensitive acrylic resinis used for the planarization film 176, thereby providing an insulatingfilm with excellent planarity. The planarization film 176 is formed overalmost all of the surface of the substrate 102 and then partly removedto form the openings used for the connection between the sourceelectrode 174 and the pixel electrode 184, the connection between thewiring 220 and the contact electrode 222, the formation of thepower-source terminal 118, and for providing high flexibility to thethird region 218 (FIG. 18A). After that, the source electrode 174 andthe wiring 220 exposed by removing the planarization film 176 areprotected by using a conductive oxide such as indium-tin oxide (ITO) andindium-zinc oxide (IZO). That is, the connection electrode 178 connectedto the source electrode 174 as well as the first contact electrode 222 aand the protection electrode 222 c connected to the wiring 220 areformed. The formation of these electrodes prevents the source electrode174 and the wirings 220 from deteriorating in the following processes.Simultaneously, the supplementary capacitor electrode 180 is formed overthe planarization film 176 (FIG. 18A).

Next, the capacitor insulating film 182 is formed to cover theconnection electrode 178, the first contact electrode 222 a, and theprotection electrode 222 c. The capacitor insulating film 182 mayinclude a silicon-containing inorganic compound, and a silicon-nitridefilm is typically employed. The capacitor insulating film 182 is alsoformed by preparing an insulating film over almost all of the surface ofthe substrate 102, followed by performing patterning with etching topartly remove the insulating film so that the top surfaces of theconnection electrode 178 and the first contact electrode 222 a, asurface of the protection electrode 222 c other than an edge portionthereof, and the wiring 220 are exposed (FIG. 18B). With this process,the terminals such as the power-source terminal 118 are fabricated.Simultaneously, the opening 188 is formed.

Next, the pixel electrode 184 is formed (FIG. 18B). The structure of thepixel electrode 184 is arbitrarily selected. For example, a three-layerstacked structure of IZO, silver, and IZO may be employed when the pixelelectrode 184 is used as a reflective electrode. The pixel electrode 184is formed so as to be electrically connected to the connection electrode178 and overlap with the supplementary capacitor electrode 180. Withthis process, the pixel electrode 184 is electrically connected to thedriving transistor 140, and the supplementary capacitor 152 isfabricated by the pixel electrode 184, the capacitor insulating film182, and the supplementary capacitor electrode 180 in the pixel 184.Moreover, the second contact electrode 222 b is simultaneously formed soas to overlap with and be electrically connected to the first contactelectrode 222 a when the pixel electrode 184 is formed.

After forming the pixel electrode 184, the partition wall (also called abank or a rib) 186 is formed (FIG. 19). Similar to the planarizationfilm 176, the partition wall 186 is formed using a photo-sensitiveacrylic resin and the like. The partition wall 186 covers the edgeportion of the pixel electrode 184 and possesses an opening exposing asurface of the pixel electrode 184 to allow the surface to function asan emission region. An edge of the opening preferably has a moderatelytapered shape. If the edge of the opening is steeply tapered, a coveragedeficiency of the EL layer 190 formed later is caused. Here, theplanarization film 176 and the partition wall 186 are in contact witheach other through the opening 188 formed in the capacitor insulatingfilm 182 therebetween. This structure allows impurities such as waterand an organic compound eliminated from the planarization film 176through a heating treatment after the formation of the partition wall186 to be released.

After forming the partition wall 186, the EL layer 190 is prepared (FIG.19). The functional layers included in the EL layer 190 may be formedwith an evaporation method or a wet-type film-formation method. Afterforming the EL layer 190, the opposing electrode 198 is formed. Here,the opposing electrode 198 is configured to exhibit a light-transmittingproperty with respect to visible light since the light-emitting element130 with a so-called top-emission structure is fabricated. For example,the opposing electrode 198 is formed by depositing an alloy of magnesiumand silver at a thickness allowing the light emitted from the EL layer190 to pass therethrough. The opposing electrode 198 is formed to covernot only the display region 106 but also the contact electrode 222 andis electrically connected to the wiring 220 via the first contactelectrode 222 a and the second contact electrode 222 b. This structureallows the power-source potential (PVDD) provided from the power-sourceterminal 118 to be supplied to the opposing electrode 198.

After forming the opposing electrode 198, the passivation film 200 isprepared. The passivation film 200 has a function to prevent impuritiessuch as water from entering the light-emitting element 130 from theoutside. As shown in FIG. 20, the passivation film 200 may have astructure in which the first layer 202, the second layer 204, and thethird layer 206 are stacked. These layers may be respectively formed asa silicon-nitride film, an organic resin film, and a silicon-nitridefilm. A silicon-oxide film or an amorphous silicon film may be furtherdisposed between the first layer 202 and the second layer 204 or betweenthe second layer 204 and the third layer 206 in order to improveadhesion.

At that time, the first layer 202 and the third layer 206 are formed soas to cover almost all of the surface of the substrate 102, while thesecond layer 204 is formed so as to cover the display region 106 and thecontact electrode 222 but not to cover the trench 132 and thepower-source terminal 118. After that, the resin film 210 is formed asshown in FIG. 21. The resin film 210 is prepared so as to selectivelycover the display region 106 and contact electrode 222. Etching isconducted using this resin film 210 as a mask to remove the first layer202 and the third layer 206 which are not covered by the resin film 210.With this process, the wiring 220 is exposed in the trench 132, and theprotection film 222 c of the power-source terminal 118 is exposed,enabling the electrical connection with the FPC 114.

Although not illustrated, a supporting film 128 is provided over theresin film 210, light irradiation is performed through the supportingsubstrate 103 to reduce adhesion between the supporting substrate 103and the substrate 102, and the supporting substrate 103 is peeled off. Asupporting film 126 is disposed after peeling off the supportingsubstrate 103, thereby providing the display device 100.

As described above, in the present embodiment, the first filler 230 andthe second filler 232 can be selectively and locally provided on theside surfaces of the undercoat 160 and over the substrate 102 close tothe side surfaces by treating the uncured resin oligomers under areduced pressure and treating the substrate 102 with the obtained vaporof the oligomers. With this structure, the steps caused by the undercoat160 can be decreased. In addition, even if the trench 132 isunintentionally formed, the first filler 230 and the second filler 232can be selectively and locally provided on the sidewalls of the trench132 and over the substrate close to the sidewalls, allowing the stepsformed by the trench 132 and the undercoat 160 to be decreased. As aresult, it is possible to prevent disconnection of the wirings forsupplying the image signals and power source. Moreover, the insulatingfilms such as the undercoat 160, the interlayer insulating film 170, andthe planarization film 176 are not arranged in the region (third region218) of the display device 100 which is to be bent, by which highflexibility can be provided to the third region 218. Additionally, nobrittle insulating film is arranged in the third region 218 which is tobe bent. Hence, reliability of the display device 100 caused by damageof these insulating films is not decreased. Accordingly, a displaydevice with high reliability can be produced at a low cost.

The aforementioned modes described as the embodiments of the presentinvention can be implemented by appropriately combining with each otheras long as no contradiction is caused. Furthermore, any mode which isrealized by persons ordinarily skilled in the art through theappropriate addition, deletion, or design change of elements or throughthe addition, deletion, or condition change of a process is included inthe scope of the present invention as long as they possess the conceptof the present invention.

In the specification, although the cases of the organic EL displaydevice are exemplified, the embodiments can be applied to any kind ofdisplay devices of the flat panel type such as other self-emission typedisplay devices, liquid crystal display devices, and electronic papertype display device having electrophoretic elements and the like. Inaddition, it is apparent that the size of the display device is notlimited, and the embodiment can be applied to display devices having anysize from medium to large.

It is properly understood that another effect different from thatprovided by the modes of the aforementioned embodiments is achieved bythe present invention if the effect is obvious from the description inthe specification or readily conceived by persons ordinarily skilled inthe art.

What is claimed is:
 1. A display device comprising: a substrate; a firstinsulating film over the substrate, the first insulating film exposing apart of the substrate to provide an exposed surface to the substrate; asecond insulating film in contact with the exposed surface and a firstside surface of the first insulating film; and a first wiring over thesecond insulating film and in contact with the exposed surface, thefirst insulating film, and the second insulating film.
 2. The displaydevice according to claim 1, further comprising a third insulating filmspaced from the second insulating film and in contact with the exposedsurface, wherein the first insulating film has a second side surfacefacing the first side surface through the exposed surface, the thirdinsulating film is in contact with the second side surface, and thewiring is located over the third insulating film and in contact with thethird insulating film.
 3. The display device according to claim 2,wherein the second insulating film and the third insulating film areapart from each other.
 4. The display device according to claim 2,wherein the first insulating film includes an inorganic compoundcontaining silicon, and the second insulating film and the thirdinsulating film each include an organic compound containing carbon,oxygen, and hydrogen.
 5. The display device according to claim 1,further comprising a second wiring adjacent to the first wiring, whereinthe first side surface has a bent portion between the first wiring andthe second wiring in a plan view.
 6. A display device comprising: asubstrate having a first region, a second region, and a trenchoverlapping with a region between the first region and second region andhaving a first sidewall and a second sidewall facing each other; a pairof first insulating films over the substrate and in contact with thesubstrate in the first region and the second region; a pair of secondinsulating films in the trench, the pair of second insulating filmsbeing spaced from each other and respectively in contact with the firstsidewall and the second sidewall; and a plurality of wirings over and incontact with the pair of first insulating films and the pair of secondinsulating films, the plurality of wirings being in contact with thesubstrate in the trench.
 7. The display device according to claim 6,wherein one of the pair of second insulating films and the other of thepair of second insulating films are apart from each other.
 8. Thedisplay device according to claim 6, wherein the plurality of wirings isin contact with a side surface and a top surface of the pair of firstinsulating films.
 9. The display device according to claim 6, wherein asurface of the pair of second insulating films in contact with theplurality of wirings is inclined from the first sidewall and the secondsidewall in a cross-sectional view.
 10. The display device according toclaim 6, wherein the pair of first insulating films overlaps with thetrench, and the pair of second insulating films is partly covered by thepair of first insulating films.
 11. The display device according toclaim 6, further comprising: a pair of third insulating films over thefirst region and the second region, respectively, and sandwiched by thepair of first insulating films and the plurality of wirings; and a pairof fourth insulating films over and in contact with the pair of firstinsulating films, respectively, the pair of fourth insulating filmsbeing in contact with the pair of third insulating films, respectively,wherein top surfaces of the pair of insulating films are exposed fromthe pair of fourth insulating films, and the plurality of wirings is incontact with the pair of third insulating films and the pair of fourthinsulating films.
 12. The display device according to claim 6, furthercomprising: a pair of third insulating films over the first region andthe second region, respectively, and sandwiched by the pair of firstinsulating films and the plurality of wirings; and a pair of fourthinsulating films in contact with surfaces of the pair of thirdinsulating films, the pair of fourth insulating films being spaced fromthe pair of first insulating films, wherein the plurality of wirings isin contact with the pair of third insulating films and the fourthinsulating films.
 13. The display device according to claim 6, whereinthe pair of first insulating films includes an inorganic compoundcontaining silicon, and the pair of second insulating films includes anorganic compound containing carbon, oxygen, and hydrogen.
 14. Thedisplay device according to claim 11, wherein the pair of thirdinsulating films includes an inorganic compound containing silicon, andthe pair of fourth insulating films includes an organic compoundcontaining carbon, oxygen, and hydrogen.
 15. The display deviceaccording to claim 12, wherein the pair of third insulating filmsincludes an inorganic compound containing silicon, and the pair offourth insulating films includes an organic compound containing carbon,oxygen, and hydrogen.
 16. The display device according to claim 6,wherein the first sidewall has a bent portion between the adjacentwirings in a plan view.
 17. A display device comprising: a substratehaving a first region, a second region, a third region sandwiched by thefirst region and the second region, a first step between the firstregion and the third region, and a second step between the second regionand the third region; a pixel over the first region; a terminal over thesecond region; an undercoat over the first region and the second region,the undercoat being arranged so that the substrate is exposed in thethird region; a first filler in contact with a first sidewall of thefirst step; a second filler spaced from the first filler and in contactwith a second sidewall of the second step; and a plurality of wiringsover the undercoat, the plurality of wirings being in contact with theundercoat in the first region and the second region and with the firstfiller, the second filler, and the substrate in the third region. 18.The display device according to claim 17, wherein the first filler andthe second filler are apart from each other.
 19. The display deviceaccording to claim 17, wherein the plurality of wirings is in contactwith a side surface and a top surface of the undercoat in the firstregion and the second region.
 20. The display device according to claim17, wherein surfaces of the first filler and the second filler incontact with the plurality of wirings are inclined from the firstsidewall and the second sidewall in a cross-sectional view.